The present invention relates to a process and apparatus for the removal of solid matter from coal tar. It is applicable to tar obtained during distillation of coal in any type of retort (such as coke ovens and gas retorts).
Tar is generally recovered from coal distillation by cooling of the raw gas from the retorts which causes condensation of water and tar followed by decantation of the condensate to separate water and tar.
It is well known that the raw gas leaving the retorts also contains a certain quantity of solid matter, normally in the form of dust which mainly consists of fine particles of carbon suspended in the gas.
In the majority of existing distillation processes this solid matter remains in the tar, in which it constitutes the major part of what is known as the solid residue of the tar. When the proportion of this solid residue is not too high its presence in the tar does not cause serious difficulties and is generally tolerated.
However in the operation of certain processes which are used more and more in modern installations (involving, for example, coal which is ground to a very fine size, charging of coal to the retorts at an increasingly low water content or even of dry coal, aspiration of charging fumes, and sealing of the condenser or condensers in order to avoid atmospheric pollution) the quantity of dust entrained in the tar becomes greater to the point where its presence constitutes a serious disadvantage which may become inacceptable.